A rare intramuscular osteolipoma: A case report

•Osteolipomas are rare and usually located in the intraosseous region or adjacent to bone.•Osteolipoma with no connection to bony structures is very unusual.•CT and MRI are useful for diagnosis but sometimes they are indistinguishable from well-differentiated liposarcomas.•Definitive diagnosis of the lesion can easily be done with histopathologic examination and treatment is by surgical excision. Lipomas are frequently presented in adults and account for almost 50% of all soft-tissue tumors. Osteolipomas are rare and usually located in the intraosseous region or adjacent to bone. It is very unusual for osteolipomas with no connection to bony structures. We report a rare intramuscular osteolipoma independent of bone tissue. We report a case of a 58-year-old man with painful and progressively enlarging mass in the right lower leg. A plain X-ray and computed tomography (CT) scans revealed a large homogeneous, low-fat density mass containing an oval shape calcification without bone connection. MRI showed a circumscribed mass in the peroneus muscle with a large calcified component. The patient underwent surgical excision of the mass. Histologically, benign osteolipoma was the final diagnosis. No recurrence was observed at six months follow-up. Lipoma is a common benign soft tissue neoplasm but osteolipoma is rare. Most cases osteolipomas are connected with bone. independent of bone tissue has been reported in very few cases. Most of them occurred in the head and neck area. The pathogenesis of osteolipoma is still not clear. Although CT and MRI are useful for differential diagnosis, care should be taken because sometimes they are indistinguishable from well-differentiated liposarcomas. Excisional biopsy is useful for definitive diagnosis. Although ossifying lipomas are very rare, it is important to keep them in mind when a lesion with adipose tissue in combination with ossification is encountered.